Cutoff values of the Inflammatory Bowel Disease Questionnaire to predict a normal health related quality of life

Abstract

One of the objectives in the treatment of the inflammatory bowel disease (IBD) is improving the patient's quality of life. However, we do not dispose of validated criteria to determine the questionnaire's scoring threshold that has to be reached in order to be able to assert that the patients' quality of life has normalized.

Objective: To determine the normality punctuation cutoff in the IBD specific quality of life questionnaire IBDQ-36.

Method: Cross-sectional study in a random sample of IBD patients, who have completed the questionnaires IBDQ-36 and EuroQol-5D. The IBDQ-36 normality was calculated according to its equivalence with the EuroQol-5D tariff ≥ 0.90, which corresponds to the 95% CI of the average obtained in a Spanish general population.

Results: 218 patients were included. According to the EuroQol-5D tariff, 70 patients were considered to have a normal quality of life and 148 a quality of life poorer than the general population. The IBDQ-36 scoring was significantly higher in the normal quality of life group (222.9 ± 22.8 vs. 171.4 ± 44.8 in the bad quality of life group, p<0.001). According to the linear regression between IBDQ-36 and EuroQol-5D, the cutoff point is 209, with a sensitivity and specificity to predict normality of 0.74 and 0.71 respectively.

Conclusions: Scores of the IBDQ-36 equal or superior to 209 suggest quality of life comparable to that perceived by the general population. This study allowed to set a threshold of normality in the management of the inflammatory bowel diseases.